1. Field of Utilization of the Invention
The present invention relates to a welding position detecting apparatus which detects by using an optical system an arc image and a groove face crossing ray image of work piece and is suitable for a welding line tracing apparatus provided in a fully automatic arc welding robot.
2. Description of Prior Art
As disclosed in Japanese Patent Laid-open Publication No. 50984/1980, there is one conventional welding position detecting apparatus which uses an optical system, in which a groove face of a work piece is irradiated with a fine laser ray which is emitted from an emitting means so as to obliquely descend and accurately converge, whereupon a reflection from the groove face is detected by a light receiving means such as an ITV camera, and a welding position on the work piece is determined by analyzing the image received by the light receiving means.
In the case of application of this apparatus to a fully automatic arc welding robot for control of a welding torch, two methods have been possible. In one method, the groove face is traced to obtain the information about the groove face and this is put in an external memory, the welding torch being controlled on the basis of this information during the welding process. In the second method, and the processes of welding and tracing the groove face surface are performed in sequence, the torch thus being controlled.
However, these methods do not ensure that the welding torch accurately traces the welding line, because, in the conventional apparatus, the tip of the welding wire is not directly observed, so that the changing amounts of extension and bending are not detected.
Another known example is disclosed in U.S. Pat. No. 4,450,339, in which a light (an arc) emitted from an arc point in a welding process is introduced into a receiving means through a group of filters, and an image obtained by the receiving means is analyzed so as to determine the point of arc emission on the tip of a welding wire.
This apparatus has enabled detection of amounts of extension and bending of the wire, but detection of the relationship between the positions of the welding torch and the work piece has still not been possible. Thus, it has not been possible to use this apparatus in detecting a welding line to be traced. It is believed that a device for detecting the position of the groove face by using the arc itself as a light source is employed together with this apparatus. However, the operation of level setting in the observation system is difficult due to the large variations in the intensity of the arc.
According to one possible idea, the apparatuses respectively shown in FIGS. 5 and 6 may be connected together to form one welding position detecting apparatus for the purpose of eliminating all the defects described above. However, the apparatus would then become too large and complicated to be used in practice.